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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 15 June

Earth and Planetary Astrophysics

Angular Momentum Transport in Protoplanetary Disks

Xue-Ning Bai

We review our current understanding on the physical processes that govern angular momentum transport and evolution of protoplanetary disks. Extremely rich in physics, these processes are intimately connected to disk gas dynamics, with profound implications for planet formation. We organize them into a three-level hierarchical framework: (1) The coupling of gas with magnetic fields and radiation sets the microphysical foundation for understanding protoplanetary disk dynamics. Key ingredients include non-ideal magnetohydrodynamic effects (requiring ionization chemistry), along with heating and cooling processes. The disk can be divided into three radial sectors governed by distinct microphysics. (2) Protoplanetary disks host diverse gas dynamical processes, including hydrodynamic, magnetic and gravitational instabilities, along with thermally and magnetically-driven disk winds. Many of these individual processes are reasonably well understood, while others still require detailed investigation. (3) Protoplanetary disks are highly complex ecosystems where multiple processes interact. It is recognized that the bulk disk exhibits weak turbulence, with magnetically-driven wind likely serving as the primary transport mechanism. However, our knowledge remains highly limited regarding the disk's innermost region, early stages, long-term evolution, and environmental effects.
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Astrophysics of Galaxies

MEGA and SMILES Find Fewer Dusty Galaxies than Expected at Cosmic Noon

Bren E. Backhaus, Allison Kirkpatrick, Kurt Hamblin et al. (+10 more)

We present infrared (IR) luminsosity functions (LFs) and resulting star formation rate densities using the JWST Mid-infrared Instrument (MIRI) observations from the MIRI EGS Galaxy and AGN (MEGA) survey and Systematic MIRI Legacy Extragalactic Survey (SMILES). JWST allows us to perform a robust analysis on the faint end of the IR LF beyond the local universe. We directly measure the 7.7$\mu$m polycyclic aromatic hydrocarbon (PAH) feature using either F1000W, F1500W, or F2100W photometry. This results in a sample of 634 galaxies across the two surveys covering an area of 105 arcmin$^2$ ($\sim$70 in the EGS and $\sim35$ in the GOODS-S/HUDF fields) and spanning $0.2<z<2$. We convert the 7.7$\mu$m PAH luminosity to total IR luminosity, resulting in LFs that are two orders of magnitude fainter than previous studies. In contrast to previous extrapolations based on shallower observations, we find a strong flattening in the faint end of the LF with an average slope of $\alpha\sim0.147$. This indicates that less luminous galaxies do not have as much dust obscured star formation as predicted. We measure the star formation rate density (SFRD) by integrating our new IR LFs and find a slightly lower SFRD in all redshift bins than previous studies made with ALMA, Herschel, and Spitzer. We also measure the contribution to the SFRD as a function of luminosity and confirm that LIRGs and ULIRGs remain the dominant contributors to the dust-obscured star formation at $z\sim1-2$.
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All authors Bren E. Backhaus, Allison Kirkpatrick, Kurt Hamblin, Kaila Ronayne, Micaela B. Bagley, Steven L. Finkelstein, Dale D. Kocevski, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Erini Lambrides, Casey Papovich, Gregory Troiani, Guang Yang

Instrumentation and Methods for Astrophysics

OpenGadget3 GPU solver tests

A. Ragagnin, G. S. Karademir, F. Groth et al. (+6 more)

We present an in-depth evaluation of the scalability and accuracy of the GPU porting of the N-body code for hydrodynamic cosmological simulations \og. While technical details of our GPU porting were presented in Ragagnin et al. (2020), in this work we focus on assessing the accuracy of the ported modules: the short range gravity integrator, the different components of the hydrodynamic solver, and the conjugate gradient solver for thermal conduction. We ran several tests that gradually increase the number of physical modules included: a gravity-only cosmological simulation; a hydrodynamical shock tube test; a non-radiative zoom-in simulation of a galaxy cluster in a cosmological box; and a full-physics zoom-in simulation of a galaxy in a cosmological box. Comparing the results obtained with the GPU implementation to those from the classical CPU version, we find excellent agreement across all tests, with small differences on very small scales. For the individual physical modules, we find a GPU chip-to-chip speedup ranging from $\approx3-5$. For more complex cosmological and hydrodynamical setups, where a large number of physical processes and overheads contribute to the total workload, the observed total chip-to-chip speedup (with the same number of nodes and CPUs per node) is $\approx2-3$. We ran our tests on four different supercomputers: Leonardo Booster (CINECA), MareNostrum-V (BSC), SuperMUC-NG2 (LRZ), and the CIP cluster of the Faculty of Physics at the Ludwig-Maximilians-Universität (LMU).
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All authors A. Ragagnin, G. S. Karademir, F. Groth, K. Dolag, L. M. Böss, T. Castro, N. Hariharan, M. Aiello, L. Tornatore

Astrophysics of Galaxies

Decoupled Kinematics and Excitation in the Compton-thick AGN NGC 6552: Spatially Resolved KOOLS-IFU Observations

Kyuseok Oh, Yoshihiro Ueda, Kanta Fujiwara et al. (+7 more)

Hard X-ray selected Compton-thick AGNs provide a relatively obscuration-resistant census of accretion, but optical line diagnostics can be strongly shaped by extinction and geometry. Spatially resolved integral-field spectroscopy can mitigate these effects and provides direct constraints on outflow kinematics and ionization state on kiloparsec scales. We present KOOLS-IFU optical integral-field spectroscopy of NGC 6552 obtained on the 3.8 m Seimei Telescope. Using spatially resolved emission-line ratios and non-parametric [O III]5007 kinematics over the central ~2 kpc, we test whether ionized-gas kinematics are locally coupled to excitation. The [O III]5007 width W80 is broadly elevated across the inner region (~530-830 km/s) and declines monotonically with projected galactocentric distance, consistent with a centrally concentrated outflow that decelerates at larger radii. Despite this clear kinematic structure, neither W80 nor the velocity asymmetry parameter dv shows a statistically significant correlation with [O III]5007/Hbeta. Order-of-magnitude outflow energetics yield Edot_K/L_bol ~ 0.01%-0.28% (for assumed n_e = 50-1000 cm^-3), consistent with [O III]-based estimates tracing only the ionized phase of a multi-phase outflow. We conclude that in NGC 6552 both the total line broadening traced by W80 and dv are consistent with being governed primarily by spatial dynamical structure and line-of-sight superposition of multiple kinematic components, with no statistically significant coupling to excitation-driven processes detected at our sensitivity level. A positive W80-[O III]5007/Hbeta coupling does emerge in the small subset of bins for which the two-component fit is most strongly favored statistically, which deeper observations will be needed to confirm.
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All authors Kyuseok Oh, Yoshihiro Ueda, Kanta Fujiwara, Keisuke Isogai, Satoshi Yamada, Keito Shimoda, Yoshiki Toba, Kazuya Matsubayashi, Shoji Ogawa, Yuya Nakatani

Earth and Planetary Astrophysics

The Effect of Adiabatic Index on Radius Evolution and the Mass Loss

Arick Collander and Eve J. Lee

Models that track the size evolution of exoplanets often assume a prescribed initial thermal state or a single adiabatic index to describe the planetary interior structure, the latter of which is taken to be $\gamma \sim1.4$ which is likely appropriate for evolved planets ($\gtrsim$1 Gyr). Extrapolating this high $\gamma$ to earlier ages (down to $\sim$million years old) is problematic since, according to thermodynamics, the adiabatic index of young planets is $\sim$1.2, which is low enough to drastically change how interior mass is distributed. We quantify the effect of varying the adiabatic index from 1.2 to 1.4 on the expected radius of the exoplanet over time. We find that envelopes of larger adiabatic indices start puffier with all else equal and undergo faster radius contraction with accelerated mass loss. Assumption of high $\gamma$ can therefore overestimate the effect of mass loss in shaping the exoplanetary population, especially when young planets are considered. We highlight the need for a more careful consideration of the initial thermal condition of planets in evolutionary models to properly interpret the radii measurements of exoplanets.
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Cosmology and Nongalactic Astrophysics

Hawai`i Supernova Flows: Bulk Flow Measurements using SNe Ia in the Optical and NIR

Aaron Do, Kaisey S. Mandel, Benjamin J. Shappee et al. (+9 more)

The present day peculiar velocity-field was sourced by primordial density fluctuations and sculpted over the lifespan of the Universe. Cosmological models such as $\Lambda$CDM make predictions for various statistical properties of peculiar velocities. Bulk flow, the average velocity within a given volume, has an expectation value of $\vec{0}$ due to isotropy, and a variance directly tied to the Hubble constant, the growth-rate of structure, and the matter power spectrum. In this paper, we use the redshifts and optical and near-infrared distance estimates to Type Ia Supernovae (SNe Ia) within subsets of the Hawai`i Supernova Flows dataset to infer the bulk flow within $z \lesssim 0.1$. The inferred speeds vary between ~100 to 400 km/s but are all consistent with the predictions of $\Lambda$CDM. As a secondary focus, we discuss the systematic uncertainty introduced by the discrete choice of methodology using two bulk flow estimators, two types of SN Ia distance estimators, and data covering two distinct regimes in wavelength space.
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All authors Aaron Do, Kaisey S. Mandel, Benjamin J. Shappee, R. Brent Tully, John L. Tonry, David Rubin, David O. Jones, Mitchell Dixon, Thomas de Jaeger, Dan Scolnic, Erik R. Peterson, Christopher R. Burns

Astrophysics of Galaxies

Chemical enrichment of the Perseus cluster core seen by XRISM/Resolve

XRISM Collaboration: Marc Audard, Hisamitsu Awaki, Ralf Ballhausen et al. (+142 more)

The intracluster medium (ICM) is rich in chemical elements, produced by core-collapse (SNcc) and Type Ia supernovae (SNIa) over the last $\sim$12 Gyr. Whereas cluster outskirts are uniformly enriched with Fe at $\sim$0.3 solar - strongly suggesting that the gas had been pre-enriched during or before the assembly of galaxies into clusters, the Fe abundance is known to centrally increase in the core of relaxed clusters. The origin of these central Fe peaks however, as well as the apparent presence of mysterious drops previously reported in the very centre of a number of systems, remain to be clarified. In this paper, we address these two questions by measuring the spatial distribution of Fe and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios in the X-ray bright, nearby Perseus cluster. We take advantage of the unprecedented spectral resolution ($\sim$5 eV) offered by the Resolve microcalorimeter on board XRISM, which observed four distinct pointings of Perseus out to $\sim$250 kpc ($\sim$0.2$r_{500}$) during its Performance Verification phase. Although the presence of an X-ray bright AGN challenges a precise quantification of absolute abundances in the very core, our baseline analysis rules out a strong drop with $>$2$\sigma$ confidence, at variance with previous CCD measurements. In addition, we find a remarkable spatial uniformity of X/Fe ratios, supporting the idea of negligible late SNIa enrichment from the brightest cluster galaxy NGC 1275. We also compare the overall chemical composition of the Perseus ICM with SNcc and SNIa nucleosynthesis yield models, finding that the co-existence of two separate SNIa enrichment channels is not needed to reproduce the ICM ratios satisfactorily.
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All authors XRISM Collaboration: Marc Audard, Hisamitsu Awaki, Ralf Ballhausen, Aya Bamba, Ehud Behar, Rozenn Boissay-Malaquin, Laura Brenneman, Gregory V. Brown, Lia Corrales, Elisa Costantini, Renata Cumbee, Maria Diaz Trigo, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan E. Eckart, Dominique Eckert, Satoshi Eguchi, Teruaki Enoto, Yuichiro Ezoe, Adam Foster, Ryuichi Fujimoto, Yutaka Fujita, Yasushi Fukazawa, Kotaro Fukushima, Akihiro Furuzawa, Luigi Gallo, Javier A. García, Liyi Gu, Matteo Guainazzi, Kouichi Hagino, Kenji Hamaguchi, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Natalie Hell, Edmund Hodges-Kluck, Ann Hornschemeier, Yuto Ichinohe, Daiki Ishi, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Jelle Kaastra, Timothy Kallman, Erin Kara, Satoru Katsuda, Yoshiaki Kanemaru, Richard Kelley, Caroline Kilbourne, Shunji Kitamoto, Shogo Kobayashi, Takayoshi Kohmura, Aya Kubota, Maurice Leutenegger, Michael Loewenstein, Yoshitomo Maeda, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Brian McNamara, François Mernier, Eric D. Miller, Jon M. Miller, Ikuyuki Mitsuishi, Misaki Mizumoto, Tsunefumi Mizuno, Koji Mori, Koji Mukai, Hiroshi Murakami, Richard Mushotzky, Hiroshi Nakajima, Kazuhiro Nakazawa, Jan-Uwe Ness, Kumiko Nobukawa, Masayoshi Nobukawa, Hirofumi Noda, Hirokazu Odaka, Shoji Ogawa, Anna Ogorzałek, Takashi Okajima, Naomi Ota, Stephane Paltani, Robert Petre, Paul Plucinsky, Frederick S. Porter, Katja Pottschmidt, Kosuke Sato, Toshiki Sato, Makoto Sawada, Hiromi Seta, Megumi Shidatsu, Aurora Simionescu, Randall Smith, Hiromasa Suzuki, Andrew Szymkowiak, Hiromitsu Takahashi, Mai Takeo, Toru Tamagawa, Keisuke Tamura, Takaaki Tanaka, Atsushi Tanimoto, Makoto Tashiro, Yukikatsu Terada, Yuichi Terashima, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Takeshi Tsuru, Ayşegül Tümer, Hiroyuki Uchida, Nagomi Uchida, Yuusuke Uchida, Hideki Uchiyama, Shutaro Ueda, Yoshihiro Ueda, Shinichiro Uno, Jacco Vink, Shin Watanabe, Brian J. Williams, Satoshi Yamada, Shinya Yamada, Hiroya Yamaguchi, Kazutaka Yamaoka, Noriko Yamasaki, Makoto Yamauchi, Shigeo Yamauchi, Tahir Yaqoob, Tomokage Yoneyama, Tessei Yoshida, Mihoko Yukita, Irina Zhuravleva, Elena Bellomi, Ian Drury, Annie Heinrich, Julie Hlavacek-Larrondo, Julian Meunier, Konstantinos Migkas, Lior Shefler, Phillip C. Stancil, Nhut Truong, Benjamin Vigneron, Congyao Zhang, John ZuHone

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Improving low-latency multi-messenger follow-up of neutron star-black hole mergers with mode-by-mode filtering

Francesco Iacovelli, Digvijay Wadekar, Javier Roulet et al. (+2 more)

Rapid parameter estimation for neutron star-black hole (NSBH) mergers is essential for deciding whether, where, and how electromagnetic facilities should follow up gravitational-wave alerts. Current low-latency analyses typically use only the dominant quadrupole harmonic, leaving strong degeneracies among luminosity distance, inclination, and intrinsic binary parameters. We show that mode-by-mode filtering of the $(2,2)$, $(3,3)$, and $(4,4)$ signal-to-noise-ratio (SNR) time series enables low-latency marginalization over higher-order-mode information at a computational cost comparable to quadrupole-only analyses. Applied to simulated NSBH detections in a LIGO-Virgo network at design sensitivity, our method improves constraints on luminosity distance, viewing angle, localization volume, and source-frame secondary mass, thereby sharpening crucial estimates of electromagnetic detectability and host-galaxy association. We also validate the approach on public data for previously detected NSBH events, finding the largest improvement for the asymmetric, higher-SNR event GW190814.
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All authors Francesco Iacovelli, Digvijay Wadekar, Javier Roulet, Emanuele Berti, Alessandra Corsi

Instrumentation and Methods for Astrophysics

The Lazuli Space Observatory: Opportunities for time-domain and multi-messenger astronomy

T. Wevers, T.J. Maccarone, A. Palmese et al. (+14 more)

Advancing time-domain and multi-messenger astronomy requires a multi-wavelength network of observatories capable of rapidly discovering, classifying, and characterizing transient phenomena. A critical gap in current capabilities is the inability to follow up faint, fast-evolving transients with sensitive, wide-band imaging and spectroscopic observations from space on timescales of minutes to hours. We discuss how the Lazuli Space Observatory will address this gap through a large collecting area, optical/NIR photometry and low-resolution integral field spectroscopy, and a rapid-response architecture with a mission requirement of $<$4 hours from trigger to first photon. Based on a latency analysis, we find a credible path to realizing response times well below this requirement, with best-case scenarios below 90 minutes under favorable conditions. We highlight extragalactic science opportunities in currently un(der)explored parts of parameter space, including gravitational wave follow-up, kilonova characterization, supernova progenitor physics, and a wide variety of fast-evolving transients and high redshift events. We further outline new observational capabilities for Galactic time-domain science, including high frequency variability in accreting systems, precision astrometry of compact objects, and the detection of compact and ultracompact binaries, enabled by high-frequency, diffraction-limited imaging and astrometry. Together, its capabilities - combining flagship sensitivity with response times one to two orders of magnitude faster than existing large space observatories - position Lazuli to make transformative contributions across time-domain and multi-messenger astrophysics.
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All authors T. Wevers, T.J. Maccarone, A. Palmese, D.J. Sand, S. Gezari, L. Rivera Sandoval, J. DiPalma, G. Hosseinzadeh, T.J. Hoyt, M. Karmen, J. Kennea, K. Kunnumkai, S. Perlmutter, M. Rigault, A. Roy, G. Stefansson, F. Yang Yang

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide

Gabriela Barenboim, Mauricio Bustamante and Qinrui Liu

Determining whether the neutrino is a Dirac or Majorana fermion remains a fundamental open question. Conventional searches rely on neutrinoless double beta decay, but this electron-only channel suffers from blind spots. We propose a new, complementary probe to overcome this limitation. A heavy neutral lepton (HNL) triggers a high-energy shift in how the active neutrino flavors ($\nu_e$, $\nu_\mu$, $\nu_\tau$) mix – but only if the neutrinos are Majorana. For GeV-scale HNLs, the upcoming beam-dump experiment SHiP can discover the HNL and measure how it mixes with the active flavors. Separately, the scattering of TeV–PeV astrophysical neutrinos can resolve the HNL, revealing a shift in the proportions of each flavor arriving at Earth that could be detected by neutrino telescopes, regardless of the unknown flavor composition at the astrophysical neutrino sources. Because this flavor shift is most sensitive to the muon and tau sectors, it bypasses the blind spots of neutrinoless double beta decay. A correlated signal at SHiP and next-generation neutrino telescopes would prove that neutrinos are Majorana; its absence would point to them being Dirac.
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Astrophysics of Galaxies

The flaring drill in the Galactic centre. Did the IRS 13 cluster carve out the mini-cavity in the mini-spiral?

Jaroslav Haas, Pavel Kroupa, Florian Peißker et al. (+1 more)

The mini-cavity is a low-density region observed in the complex of streams of ionized gas around the Galactic central supermassive black hole, Sgr A$^\star$, known as the mini-spiral. Its near-circular shape is suggestive of a formation due to the effect of stellar winds. No suitable stars are currently observed within the mini-cavity, however. In this study we assessed whether the mini-cavity could have been formed by the winds of the stars from the neighbouring IRS 13 cluster that were located at the position of the mini-cavity in the past but moved away from it later on owing to their orbital motions around Sgr A$^\star$. Furthermore, we estimated the rate of accretion of the then-abundant interstellar medium onto the putative intermediate-mass black hole that has been proposed to reside in the IRS 13 cluster and the corresponding X-ray luminosity of this black hole. The estimates were obtained analytically using the astrophysical properties reported for the involved objects and the environment. Based on our results, we suggest that the mini-cavity was formed by the winds of the IRS 13 cluster member stars about 300 years ago, when this cluster went through the Bar region of the mini-spiral. The accompanying accretion of the interstellar medium onto the putative intermediate-mass black hole in this cluster may have produced multiple X-ray flares with luminosities of $\approx10^{39}$ erg/s. Such flares are compatible with the X-ray reflections currently observed on the molecular clouds in the complexes Sgr A, B, and C, including the necessary light-travel time delay.
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All authors Jaroslav Haas, Pavel Kroupa, Florian Peißker, Mark R. Morris

Solar and Stellar Astrophysics

On the Robustness of Bi-Stability Jump Predictions

Jorick S. Vink, Gautham N. Sabhahit and Andreas A. C. Sander

The bi-stability jump is a long-standing theoretical prediction of radiatively driven wind theory, associated with Fe IV/III recombination around T = 21000 - 25000 K. While most theoretical approaches predict a strong increase in mass-loss rates across the bi-stability jump, most empirical mass-loss studies of OB supergiants have not revealed the expected signature. We computed new hydro-dynamically consistent PoWR models at low and intermediate Eddington parameters to test whether the bi-stability jump persists in the canonical B supergiant regime. The PoWR models presented here predict a robust bi-stability jump, with an increase in mass-loss rate by more than an order of magnitude and a simultaneous drop in terminal wind velocity in line with Monte Carlo models and other co moving frame (CMF) calculations. The jump coincides with a transition in the dominant line driver from Fe IV to Fe III. The presence of the bi-stability jump is not restricted to high Gammae objects and remains present for models well below the LBV/hypergiant regime. The persistence of the bi-stability jump in hydro-dynamically consistent models at lower Gammae supports the interpretation of the bi-stability jump as a temperature-driven ionisation effect that operates once a stationary line-driven wind solution exists. The continuing discrepancy between predictions and empirical population studies motivates further code comparison work and controlled observational tests using individual objects such as LBVs.
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High Energy Astrophysical Phenomena

Constraints on Late-Time Flaring from Luminous Fast Blue Optical Transients using the Transiting Exoplanet Survey Satellite and the Zwicky Transient Facility

Rahul Jayaraman, Anna Y. Q. Ho, Michael M. Fausnaugh et al. (+14 more)

The Luminous Fast Blue Optical Transient (LFBOT) AT2022tsd exhibited minutes-timescale optical flares in the tens of days following the initial transient event, likely due to a central engine – either an accreting black hole or a magnetar. In this paper, we use data from the Transiting Exoplanet Survey Satellite (TESS) and the Zwicky Transient Facility (ZTF) to constrain the occurrence of similar flares in the 12 (of 14) known LFBOTs that had observational coverage with TESS from tens of days to thousands of days after the transient's initial emission. We find seven flare-like signals at the locations of four unique LFBOTs; all seven can likely be attributed to a solar system object (SSO) moving through the TESS aperture. Assuming all seven flares arise from SSOs, for the LFBOT AT2024qfm we rule out flaring with a similar timescale (40–65 d) and luminosity ($\nu L_\nu\sim10^{43}$ erg s$^{-1}$) as in AT2022tsd, while for AT2022tsd itself we rule out flares between 380–430 d after the initial transient that were as luminous as the earlier flares. This observation suggests that the engine power in AT2022tsd declined or shut off on a timescale of hundreds of days. We also find that there is no late-time activity detectable in TESS thousands of days after the prototype LFBOT, AT2018cow. We discuss our constraints on the duty cycle of such flaring and then present estimates for the number of minutes-duration flares detectable with ongoing and upcoming high-cadence ($\ll1$ d) wide-field surveys.
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All authors Rahul Jayaraman, Anna Y. Q. Ho, Michael M. Fausnaugh, Eran Ofek, Daniel A. Perley, Ruslan Konno, Martti Kristiansen, Tracy X. Chen, Michael W. Coughlin, Steven L. Groom, George Helou, K.-Ryan Hinds, Mansi M. Kasliwal, Zoë McGrath, Josiah N. Purdum, Argyro Sasli, Jesper Sollerman

Earth and Planetary Astrophysics

Simultaneous Tricolor Video Observations of Three Tiny Near-Earth Asteroids with Sub-Minute Rotation Periods

Jin Beniyama, Ryou Ohsawa, Shigeyuki Sako et al. (+4 more)

Studying the physical properties of near-Earth asteroids (NEAs) is crucial for understanding their dynamical histories and origins, and assessing impact hazards to Earth. Tiny NEAs with diameters smaller than 100 m are intrinsically faint and are typically observable only during close approaches, resulting in few well-characterized objects. Furthermore, because these objects are often fast-moving and fast-rotating, sequential multiband photometry is prone to systematic offsets in derived colors. To mitigate this effect, we performed simultaneous $g$-, $r$-, and $i$-band photometry of three tiny NEAs using the TriColor CMOS Camera and Spectrograph (TriCCS) on the 3.8 m Seimei Telescope. We used high-cadence video observations with exposure times of 1 s and 5 s to investigate lightcurve variations on timescales of seconds. All three NEAs are confirmed as fast rotators with rotation periods shorter than 60 s: $15.281\pm0.002$ s for 2021 TY$_{14}$, $21.099\pm0.003$ s for 2021 UW$_{1}$, and $8.779\pm0.013$ s for 2022 GQ$_{1}$. The derived colors indicate that 2021 TY$_{14}$ belongs to the X-complex, while 2021 UW$_{1}$ and 2022 GQ$_{1}$ belong to the S-complex. Their positions in the diameter–rotation period diagram show that all three objects belong to the small, fast-rotating NEA population, with 2022 GQ$_{1}$ being the smallest and fastest-rotating among them with spectroscopic measurements. Analysis of the color time series suggests that the surfaces of observed NEAs are largely homogeneous, although 2021 TY$_{14}$ exhibits statistically significant $g-r$ color heterogeneity with a projected spot fraction of approximately 50%. For 2021 UW$_{1}$, minor localized variations of up to $\sim20$% in composition cannot be ruled out.
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All authors Jin Beniyama, Ryou Ohsawa, Shigeyuki Sako, Satoshi Takita, Daisuke Kuroda, Tomohiko Sekiguchi, Keisuke Isogai

High Energy Astrophysical Phenomena

Fermi-eROSITA cross-correlations suggest annihilation lines of $\sim70$ GeV WIMPs

Uri Keshet

The deep potential wells of galaxy clusters provide some of the strongest constraints on the velocity-dependent ($p$-wave) annihilation of weakly interacting massive particle (WIMP) dark matter. Cross-correlating high-latitude Fermi-LAT 16.3-year data with the western Galactic hemisphere eROSITA map facilitates high-sensitivity tests. A blind composite matched-filter scan of the cross-correlated spectrum for the $\chi\chi\to\gamma\gamma$, $\gamma Z$, and $\gamma h$ annihilation-line triad of a single WIMP $\chi$ finds $m_\chi c^2\simeq71.9$ and $67.5$ GeV triads, each with a local $Z$-score $\sim3$ and a (henceforth global) $1.6\sigma$ (trial-corrected by pixel shuffles; $1.8$-$2.1\sigma$ in Monte Carlo and analytic estimates), insensitive to details of detrending, sky masks, and filters. Scanning for the line nonad of two cross-annihilating WIMPs finds $66.4$ and $71.9$ GeV masses (with a weak $69.2$ GeV cross-annihilation triad) at $2.3\sigma$. The leading $\sim72$ GeV triad coincides with the mass implied by interpreting the recently reported $\sim43.2$ GeV $\gamma$-ray line in three nearby clusters as its $\gamma Z$ channel. At this externally fixed mass, the triad reaches $3.0\sigma$ alone, and $5.1\sigma$ when combined with the reported line ($3.9\sigma$ under alternative assumptions). The triad, absent from the ambient (X-ray-uncorrelated) spectrum, presents in different Galactic sectors, strengthens under cosmological (positive) but not negative redshift broadening $\Delta z$, and peaks at $\Delta z\simeq 0.05$, consistent with expectations; its two non-$43$ GeV channels reach $2.3\sigma$ by themselves. Measured (not loss-corrected) intrinsic cross sections are a few $10^{-19}$ cm$^3$ s$^{-1}$ for WIMPs tracing the X-ray gas.
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High Energy Astrophysical Phenomena

Curvature–Radiation Geometries Across the Second CHIME/FRB Fast Radio Burst Population

Thonimar V. Alencar, Jéferson A. S. Fortunato and Wiliam S. Hipólito-Ricaldi

We present a population-level spectral analysis of fast radio bursts from the second CHIME/FRB catalog using three curvature-radiation-motivated templates: point-source, one-dimensional bunch, and paired-bunch cavity models. Fits are evaluated with reduced chi-squared $\chi^2_r$, AIC/BIC, and the Ljung-Box residual autocorrelation test. All three templates yield median $\chi^2_r$ values close to unity for both repeating and non-repeating bursts. Repeaters show narrower $\chi^2_r$ distributions than non-repeaters, with statistically significant but modest population-level differences. AIC favours the one-dimensional bunch model for the largest fraction of sources, whereas BIC increases the relative preference for the simpler point-source model. However, residual autocorrelation remains widespread across all models: only 15%-21% of sources simultaneously satisfy goodness-of-fit and residual-independence criteria, indicating persistent structured residuals beyond the tested templates. These results suggest that while curvature-radiation-motivated geometries capture the dominant spectral envelope of many FRBs, additional physical ingredients or spectral components are required to describe the fine-scale spectral structure of the data. The inferred coherence scales are $\sim$16-18 cm for the one-dimensional model and $\sim$25-28 cm for the cavity model.
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Solar and Stellar Astrophysics

Systematic and Statistical Uncertainties in Cepheid PL Relations: Incorporating a Cross-Filter Random-Phase Mitigation Approach

Mahdi Abdollahi and Atefeh Javadi

The Period-Luminosity (PL) relation of Cepheid variable stars is a fundamental tool for measuring extragalactic distances and constraining the Hubble constant (H0). Achieving high precision in PL based distances requires careful consideration of both systematic and statistical uncertainties. We review the main sources of these uncertainties in PL relations, highlighting the increasing impact of random-phase errors in single-epoch observations from limited temporal coverage, such as those obtained with the James Webb Space Telescope (JWST). We discuss mitigation strategies for systematic errors, including photo metric calibration offsets, metallicity effects, blending, and parallax biases, and quantify key contributors to statistical errors, such as photometric noise, intrinsic scatter, and phase-sampling limitations. Special attention is given to a recently proposed cross-filter random-phase correction method (Abdollahi et al., 2025), which recovers mean magnitudes from single-epoch data by exploiting correlations between PL residuals in different bands. This technique reduces the dispersion in the infrared PL relation by 28%, equivalent to an order-of-magnitude increase in effective temporal sampling, demonstrating an efficient path to improving Cepheid-based distance measurements and the precision of H0.
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Astrophysics of Galaxies

Mapping a Quasar Outflow from Parsec to Kiloparsec Scales: A Combined HST Absorption and VLT Emission Investigation

Mayank Sharma, Travis C. Fischer, Manuela Bischetti et al. (+4 more)

Linking nuclear winds to galactic-scale outflows remains a major observational challenge in understanding the multiscale physics of active galactic nuclei feedback. Here we present VLT/KMOS integral-field spectroscopy and SDSS observations of the $z = 0.9655$ quasar PKS J0352$-$0711. Our analysis reveals complex, multi-ionization emission, including a fast, unresolved nuclear wind and a spatially resolved galactic-scale outflow. We integrate the [O III] emission properties with those deduced from the mini-broad-absorption-line outflows detected in HST/COS observations of this quasar. This unique combination of datasets allows us to trace, for the first time, the physical progression of a quasar outflow from $\sim$ 10 pc to 10 kpc. The multiscale kinematics support a unified evolutionary scenario where the inner, constant-velocity ($\sim-3800 \textrm{ km s}^{-1}$) expansion of the wind is traced jointly in absorption ($\sim 9$ pc) and emission ($\gtrsim 40$ pc). As the wind propagates to $\sim$ 500 pc, the intermediate absorption system reveals a deceleration to $\sim-2100 \textrm{ km s}^{-1}$, consistent with mass-loading from the interstellar medium. Finally, our spatially resolved observations capture the gas breaking out of the inner galaxy, in the form of a wide-angle blueshifted outflow expanding beyond 8 kpc, with a velocity of $\sim -1000 \textrm{ km s}^{-1}$. Despite the three orders of magnitude variation in spatial scale, and a factor-of-four deceleration, the momentum fluxes remain consistent within uncertainties across all scales. These results suggest that the distinct outflow components represent the integrated history of a sustained feedback cycle from nuclear to galactic scales.
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All authors Mayank Sharma, Travis C. Fischer, Manuela Bischetti, Nahum Arav, Fabrizio Fiore, Chiara Feruglio, Manoj Ghosh

Astrophysics of Galaxies

Detection of C$_{60}$ Combination Bands in the Near-IR Spectrum of Tc 1

Morgan M. Giese, Vincent J. Esposito, Simon Van Schuylenbergh et al. (+26 more)

We report the detection of a set of new near-infrared emission features between 3.5 and 5.2 ${\mu}$m in JWST/NIRSpec observations of Tc 1, the planetary nebula known for displaying the cleanest and most prominent mid-infrared cosmic fullerene spectrum. These broad features share the same spatial distribution as the well-known C$_{60}$ and C$_{70}$ mid-infrared emission bands, peaking in an asymmetric ring approximately 5-6" from the central star. Through comparison with new anharmonic quantum chemical calculations, we demonstrate that these features arise from C$_{60}$ combination bands, marking their first detection in an astrophysical environment. The total energy radiated in the combination bands amounts to ~17% of the total energy emitted from all C$_{60}$ modes, with direct implications for fullerene cooling models. These near-infrared combination bands offer a promising new window for identifying and studying the molecular astrophysics of C$_{60}$ in sources where mid-infrared spectra are more complex.
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All authors Morgan M. Giese, Vincent J. Esposito, Simon Van Schuylenbergh, Jan Cami, Els Peeters, Charmi Bhatt, Dries Van De Putte, A. G. G. M. Tielens, Michael J. Barlow, Jeronimo Bernard-Salas, Alessandra Candian, Bryan Changala, Nick L. J. Cox, Harriet L. Dinerstein, D. A. García-Hernández, Marco A. Gómez-Muñoz, Kay Justtanont, Kathleen E. Kraemer, Eric Lagadec, Arturo Manchado, Ana Monreal Ibero, Raghvendra Sahai, Ameek Sidhu, G. C. Sloan, N. C. Sterling, Jeremy R. Walsh, Roger Wesson, Joshua Cole Whitman, Albert Zijlstra

Instrumentation and Methods for Astrophysics

Graph Neural Networks Trained on Null Signal for Angle Reconstruction in X-ray Polarimetry

Vittorio Latorre, Victor Rodriguez-Fernandez, Alessandro Di Marco et al. (+3 more)

Scientific real detectors often produce sparse, irregular data defined on non-Euclidean domains, where conventional convolutional neural networks (CNNs) impose geometric biases that distort physical observables. In X-ray polarimetry, such distortions can mimic polarization signals at the percent level, critically limiting measurement fidelity. We consider a framework based on Graph Neural Networks (GNNs) for reconstructing photoelectron emission angles from Gas Pixel Detectors, operating directly on their native sparse hexagonal topology. The network is trained solely on unpolarized simulated data and integrates rotational data augmentation, ensemble averaging, and modulation-aware model selection to reduce spurious angular modulation. Despite never encountering polarized examples, the model is able to recover the overall structure of polarized signals. Compared with the classical Method of Moments (MoM), an analytical approach to track angle reconstruction, the proposed GNN achieves lower per-track error but yields worse performance for polarimetry, revealing a mismatch between local reconstruction accuracy and global polarimetric performance. Compared to CNN-based approaches, the framework shows competitive performance on both unpolarized and polarized reconstructions, despite being trained in a more challenging power-law energy distribution. These results position the method as a diagnostic tool to highlight the limitations and trade-offs of learning-based approaches for X-ray-polarimetry signal reconstruction.
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All authors Vittorio Latorre, Victor Rodriguez-Fernandez, Alessandro Di Marco, Fabio La Monaca, Fabio Muleri, Paolo Soffitta

Astrophysics of Galaxies

Magnetic Fields in Massive Star-forming Regions (MagMaR). VII. On the dynamical importance of B-fields in massive protocluster W33 A

Fengwei Xu, Q. Zhang, P. Sanhueza et al. (+30 more)

Magnetic fields (B-fields) are likely important in massive protocluster formation, but their role remains poorly constrained. We present 1.2 mm ALMA full-polarization observations of W33 A, a massive star-forming region at 2.4 kpc, with an angular resolution of 0.3 arcsec (730 au). The region is resolved into 20 dense cores and 9 filaments. The plane-of-sky B-field, inferred from linearly polarized dust emission, shows diverse structures: two nearly perpendicular large-scale components oriented northwest-southeast (NW-SE) and northeast-southwest (NE-SW), and two localized features toward the millimeter peaks MM1 and MM2. The NW-SE component could be shaped by a molecular outflow. The NE-SW component is coherent along the main filaments F1, F-Main, and Tail, all of which show trans-Alfvenic turbulence. In F-Main, the line mass exceeds the turbulent critical value, implying that magnetic support is required to prevent radial collapse and suppress fragmentation. In F1 and Tail, turbulence alone can support the gas against gravity, although B-fields may provide additional support. Toward MM1, the B-field follows a spiral-like infalling streamer traced by CH3CN. The trans-Alfvenic state of the accreting gas suggests efficient magnetic damping of turbulence and a magnetically regulated, laminar accretion flow feeding the core. Toward MM2, the B-field shows an hourglass morphology fitted by parabolic curves. Two independent methods give a consistent field strength of about 8.1(1.9) mG, and virial analysis indicates that the B-field is dynamically important in delaying collapse of MM2. Within a single protocluster, B-fields can stabilize filaments, regulate accretion, and delay core collapse, highlighting their diverse dynamic role in high-mass star formation.
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All authors Fengwei Xu, Q. Zhang, P. Sanhueza, K. Wang, Hauyu Baobab Liu, H. Beuther, Wenyu Jiao, C. Wang, P. C. Cortés, P. M. Koch, J. M. Girart, M. T. Beltrán, J.-W. Wang, J. Liu, F. A. Olguin, Xing Lu, S. Li, Pak Shing Li, T. Liu, K. Morii, J. Hwang, H.-R. V. Chen, S. Jiao, Y. Cheng, Q. Luo, Piyali Saha, Ji-hyun Kang, C. Y. Law, L. K. Dewangan, O. R. Jadhav, E. J. Chung, Chakali Eswaraiah, Luis A. Zapata

Cosmology and Nongalactic Astrophysics

Analytic results for slow-roll curved-space inflation and exponential potentials

Dimitrios Tsimpis and Govind Venugopal

We derive analytic templates for the scalar and tensor primordial power spectra describing cosmologies that transition from kinetic dominance to slow-roll inflation in the presence of spatial curvature. Our results extend recent works in the literature, allowing us, in particular, to recover the scalar and tensor tilts analytically. We revisit the case of curvature-assisted single-exponential models in light of this framework. In the case of an open universe, the phase space of such models naturally includes cosmologies that start out in a kinetic-dominance regime followed by a parametrically controlled quasi-de Sitter phase. However, they do not fit in the framework of the templates, as their second Hubble slow-roll parameter remains of order one in the quasi-de Sitter regime.
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Earth and Planetary Astrophysics

Tidal Rock Grinding as a Source of H2 on Enceladus

Karin I. Oberg, Cara Magnabosco and Nicholas J. Tosca

The Solar System hosts multiple potentially habitable environments, including the subsurface ocean beneath the icy crust of Saturn's moon Enceladus. This ocean's composition is unusually well constrained thanks to Cassini's observations of Enceladus's south polar plume during multiple flybys. Among the plume's more surprising components is molecular hydrogen (H2), detected in trace amounts. The presence of observable amounts of H2 is intriguing not only because it is difficult to explain through conventional geochemical processes, but also because it could serve as both an energy source for life and a driver of prebiotic organic chemistry. In this study, we explore whether tidally induced rock grinding within Enceladus's core could account for the observed H2. Laboratory experiments show that H2 can be efficiently produced when freshly fractured rock reacts with water. Using these experimentally determined production efficiencies, we estimate H2 generation rates as a function of the fraction of tidal energy dissipated through rock grinding. Our results suggest that tidal grinding could plausibly produce the observed levels of H2, with instantaneous production rates potentially exceeding those from radiolysis or serpentinization. However, sustaining such production over geological timescales would require efficient healing of silicate surfaces in the core to allow repeated grinding. Without such healing, tidally induced rock grinding may instead lead to episodic bursts of chemical activity lasting up to millions of years–potentially sufficient to initiate new prebiotic pathways. This transient mechanism would complement the longer-term, lower-energy contributions from serpentinization (over hundreds of millions of years) and radiolysis (over billions of years).
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Astrophysics of Galaxies

Optically Invisible Galaxies at Cosmic Noon and beyond with JWST/UNCOVER

Pralay Biswas, Rashi Jain and Yogesh Wadadekar

The traditional selection bias in high-redshift galaxy surveys toward rest-frame ultraviolet emission has constrained our understanding of the high-redshift universe by systematically excluding optically faint (observer-frame) galaxies. Utilising JWST UNCOVER and MegaScience data of the Abell 2744 cluster field, we identify 113 high-redshift ($z > 2$) and 94 low-redshift ($z < 2$) HST-dark galaxies using a red $1.50-3.56 \ \mu$m color criterion. Their physical properties were derived using multiwavelength photometry from 20 JWST/NIRCam and 7 HST filters. Unlike classical submillimeter and Spitzer-selected HST-dark galaxies that primarily identify the most massive, dusty, highly star-forming galaxies, our study uncovers a moderately dusty population across a significantly broader range of stellar mass and star-formation rate. Leveraging gravitational magnification and ultra-deep JWST imaging, we found HST-dark galaxies with a stellar mass as low as $10^{7.5}$ at $z>2$. These galaxies have smaller sizes and follow the star-forming main sequence. Our analysis reveals a prominent peak in the Star Formation Rate Density at $z \approx 4.5$ ($9.89^{+6.93}_{-4.34} \times 10^{-3} \, M_{\odot} \, \text{yr}^{-1} \, \text{Mpc}^{-3}$). We also characterise a sub-population at $z < 2$ of Highly Extincted Low-Mass analogues with extremely low stellar masses (median $\log M_{\star}/M_{\odot} \approx 7.10$) and high dust extinction (median $A_V \approx 1.97$ mag). Our sample demonstrates the unique power of JWST to reveal this previously missing galaxy population and to provide a more complete census of galaxies in the high-z universe.
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Cosmology and Nongalactic Astrophysics

The cosmic tetrarchy: four estimators breaking the assumption degeneracy in cosmological distance tensions

Matteo Martinelli and Domenico Sapone

The origin of cosmological distance tensions remains a central open question in precision cosmology, complicated by the fact that most consistency tests between datasets cannot isolate which physical assumption is responsible for an observed discrepancy. We address this by reformulating the standard cosmological framework as a single null test: the requirement that the dimensionless sound-horizon ratio $r_{\rm d}/r^{\rm fid}_{\rm d}$ be one redshift-independent number. We show that this test admits four complementary measurements, obtained by combining Baryon Acoustic Oscillation (BAO) data with either Type Ia supernovae (SNIa) or cosmic chronometers (CC), in either the transverse or the radial direction. The four channels rely on distinct subsets of physical assumptions — distance-ladder calibration, the distance duality relation, spatial flatness, and the standard-ruler picture — and one of them, the radial CC-anchored channel, requires none and serves as the natural reference of the framework. The pattern of agreement or disagreement among the four therefore localises the assumption responsible for any observed tension. We refer to this fourfold decomposition as the cosmic tetrarchy and evaluate it on DESI DR2 BAO data combined with Pantheon+ and cosmic chronometers, using both a binned analysis with full analytic covariance propagation and a non-parametric Gaussian Process reconstruction. We find that current data are compatible with a single, redshift-independent sound-horizon scale; when comparing the different estimators, we find hints of discrepancies between those based on SNIa and those relying on CC, although with a lack of statistical significance, which might hint to a manifestation of the Hubble tension or to the breaking of assumptions such as the distance duality relation.
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Astrophysics of Galaxies

Oxygen in the protostellar clump OMC-2 FIR4

Jorma Harju, Paola Caselli, Rolf Güsten et al. (+6 more)

Atomic oxygen (OI), OH, H2O, and CO are the main carriers of oxygen in dense interstellar gas and important coolants of shocks associated with protostellar outflows. We determine the relative abundances of these species in the warm inner parts of the protostellar clump OMC-2 FIR4 in Orion A. The clump contains several young stellar objects. The upGREAT receiver including the High Frequency Array (HFA, operating at 4.74 THz, 63 micron) onboard the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA) was used to observe OMC-2 FIR4 in the lines of OI, OH, OD, HDO, and CO. Additional HDO lines were observed with the Atacama Pathfinder Experiment (APEX). Archival H2O and CO spectra observed by the Herschel satellite were included in the analysis. The observed lines were reasonably well reproduced by an expanding spherical shell model. The OI spectrum at 63 micron towards OMC-2 FIR4 is dominated by a broad line component, on top of which medium-wide and narrow line components can be discerned. The same components are present in the OH, H2O, and high-J CO spectra towards this source. We find that OI is more abundant than H2O in the shocked gas. In the broad line component, the following abundance ratios are derived: OI/H2O ~ 700, OI/OH ~ 300, OI/CO ~ 4. The high relative abundance of atomic oxygen there suggests an origin in dissociative J-shocks that are associated with strong ultraviolet radiation. The OI/CO ratio decreases below unity in the components with a smaller velocity dispersion, and these components also have higher abundances of H2O than the broad line component, although remaining below that of CO. The HDO/H2O ratio in the low-velocity components corresponds to the average ratio in the icy mantles of dust grains, and the presence of water there could also be understood in terms of sublimation without invoking high-temperature chemistry.
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All authors Jorma Harju, Paola Caselli, Rolf Güsten, Helmut Wiesemeyer, Sandra Brünken, Marc Mertens, Olli Sipilä, Jürgen Stutzki, Friedrich Wyrowski

High Energy Astrophysical Phenomena

From Morphology to Variability: Radiative Cooling Effects on Horizon-Scale Polarization in Two-Temperature GRMHD Simulations

Jane SiNan Long, Akhil Uniyal, Mingyuan Zhang et al. (+4 more)

Polarization signatures provide a new window to investigate the effects of radiative cooling in the horizon-scale accretion flows. Morphology and variability of polarization offer quantifiable diagnostics of how cooling modifies the polarised emission from two-temperature GRMHD simulations. We find that cooling enhances the effective Faraday depth, leading to stronger large-scale Faraday scrambling, particularly at higher accretion rates. In contrast, depolarization associated with higher-order photons is comparable between cooling and non-cooling models. Radiative cooling also increases the intrinsic asymmetry in both the ring structure and the polarization pattern. This effect is quantified by enhanced power in non-axisymmetric azimuthal modes ($\beta_m$, $m \neq 2$) relative to the dominant quadrupolar component $\beta_2$. The increased asymmetry is directly linked to stronger temporal variability of the polarization angle $\angle\beta_2$, including frequent sign reversals that are absent in non-cooling models. The radial profile of $\angle \beta_2$ further localizes the physical origin of these effects, distinguishing regions dominated by Faraday rotation from those influenced by photon ring contributions, and providing a clear separation between cooling and non-cooling cases. Additional tests including a non-thermal electron population indicate that the polarization structure at 230 GHz is largely insensitive to the detailed form of the electron distribution functions. Our results demonstrate that horizon-scale polarization asymmetry, variability, and radial structure encode robust signatures of radiative cooling. These findings highlight the diagnostic power of time-resolved polarimetry and high-resolution imaging for constraining radiative processes in black hole accretion flows with EHT-like observations.
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All authors Jane SiNan Long, Akhil Uniyal, Mingyuan Zhang, Yosuke Mizuno, Ziri Younsi, Christian M. Fromm, Kinwah Wu

High Energy Astrophysical Phenomena

Detection and luminosity-dependent evolution of the high-energy hump in the Be/X-ray pulsar 1A 1118-61

Alexander Salganik, Sergey S. Tsygankov, Sergey V. Molkov et al. (+12 more)

Context. Accreting X-ray pulsars exhibit strong luminosity-dependent changes in their broad-band spectra. At high luminosities, their spectra are usually described by a power-law continuum with a high-energy cutoff, whereas low-luminosity observations have revealed a two-hump spectral morphology. Aims. We aim to trace the luminosity-dependent spectral evolution of the Be/X-ray pulsar 1A 1118-61 and to constrain the luminosity range over which the high-energy hump becomes clearly distinguishable. Methods. We use dense SRG/ART-XC and Insight-HXMT monitoring, together with three broad-band NuSTAR observations of 1A 1118-61 obtained during its 2026 outburst, to trace the luminosity-dependent evolution of the spectral shape. The ART-XC data follow the decay from a peak luminosity of $\simeq7\times10^{37}$ erg s$^{-1}$ to a low-luminosity plateau at $\simeq(3$-$8)\times10^{35}$ erg s$^{-1}$ in the 4-35 keV band, while the NuSTAR observations provide broad-band spectra during the bright phase, the decline, and the plateau. We describe the continuum with a phenomenological two-component Comptonization model. Results. As the source faded, the broad-band continuum developed a distinct high-energy hump, giving rise to a two-hump morphology with broad maxima near $\sim$10 keV and $\sim$30-40 keV. The ART-XC monitoring constrains the transition to this morphology to $L_{4-35}\simeq(0.8$-$1.8)\times10^{36}$ erg s$^{-1}$. We also find a break in the luminosity dependence of the flux ratio between the two continuum humps around $L_{4-35}\sim10^{37}$ erg s$^{-1}$. A cyclotron line at $\simeq55$ keV is detected in the high-energy hump, with no significant luminosity dependence of its centroid energy. We discuss this behavior in the context of resonant interactions in the magnetized accretion flow.
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All authors Alexander Salganik, Sergey S. Tsygankov, Sergey V. Molkov, Hua Xiao, QingChang Zhao, Long Ji, Alexander A. Mushtukov, Igor Yu. Lapshov, Alexander A. Lutovinov, Alexey Yu. Tkachenko, Hua Feng, Shuang-Nan Zhang, Xiao-Bo Li, Shu Zhang, Juri Poutanen

Astrophysics of Galaxies

A HINSA view of cosmic-ray ionization in IC 348 and NGC 1333: evidence for a strong low-energy cosmic-ray disparity

Gan Luo, Marco Padovani, Daniele Galli et al. (+5 more)

The cosmic-ray ionization rate (CRIR) is one of the fundamental parameters influencing the chemical and dynamical evolution of molecular clouds. Although observations in recent years have revealed high CRIR values in massive star-forming regions and in the vicinity of protostars, the sources and acceleration mechanisms of cosmic rays remain uncertain. In this work, we present our new estimates of CRIR using the HI narrow self-absorption (HINSA) technique towards two nearby low-mass star-forming clouds, IC 348 and NGC 1333. In both clouds, the CRIR decreases with increasing H$_2$ column density, but IC 348 exhibits values that are roughly an order of magnitude higher than those in NGC 1333. To interpret this contrast, we model the low-energy spectrum of CRs in a finite slab attenuation framework, using additional constraints from the high-energy CR spectrum inferred from Fermi $\gamma$-ray observations. The best-fit spectra reproduce the observed CRIR profiles and the contrast between IC 348 and NGC 1333 suggests an order of magnitude difference in low-energy CR populations, likely originating from local acceleration sources beyond protostars (e.g., stellar-wind termination shocks), and partly from the same sources responsible for the GeV $\gamma$-ray excess. Although uncertainties in cloud structure and gas density may affect the absolute CRIR values, they do not erase the pronounced disparity between the two regions.
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All authors Gan Luo, Marco Padovani, Daniele Galli, Thomas G. Bisbas, Brandt A. L. Gaches, Di Li, Marko Krčo, Ningyu Tang

Earth and Planetary Astrophysics

Metal Oxide Clusters in Gas Giant Exoplanet Atmospheres

Deepak Bisht, Christiane Helling, David Gobrecht et al. (+6 more)

This study investigates the thermal stability and absorption of metal oxide clusters in exoplanetary atmospheres. Utilizing our thermochemical data, we analyze eight distinct cluster families: magnesium oxide (MgO), silicon monoxide (SiO), titanium monoxide (TiO), vanadium monoxide (VO), titanium dioxide (TiO$_2$), vanadium dioxide (VO$_2$), aluminum oxide (Al$_2$O$_3$), and vanadium pentoxide (V$_2$O$_5$). Equilibrium cluster populations as a function of gas temperature and pressure reveal distinct stability regimes. Under solar elemental abundances, (TiO$_2$)$\rm\rm_N$ and (Al$_2$O$_3$)$\rm_N$ are favored at higher temperatures, while (MgO)$\rm_N$ and (SiO)$\rm_N$ dominate at lower temperatures. Computed absorption spectra exhibit strong size- and composition-dependent absorption features in the mid-infrared (8–50~$\mu$m), many of which fall within the wavelength range accessible to JWST/MIRI. We further coupled cluster thermodynamics with 3D general circulation model (GCM) outputs to investigate the cluster stability across the ultra-hot Jupiters (UHJs) WASP-121 b and WASP-18 b, the hot Jupiter (HJ) WASP-39 b, and the warm Jupiter (WJ) WASP-69 b. In WASP-121 b and WASP-18 b, extreme dayside temperatures suppress large-cluster stability, yielding atmospheres dominated by metal ions at low pressures and neutral metals at depth, with limited cluster survival on the nightside and morning terminator. In WASP-39 b, larger clusters are not thermochemically favoured despite the enhanced metallicity; instead, equilibrium chemistry stabilises smaller species, with only TiO showing a tendency toward stable larger cluster forms, likely due to its open d-orbitals. In contrast, WASP-69 b favors the formation of larger metal oxide clusters across an extended pressure range, highlighting WJs as a favorable environment for metal oxide cluster stability.
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All authors Deepak Bisht, Christiane Helling, David Gobrecht, Ludmila Carone, Helena Lecoq-Molinos, Peter Woitke, Markus Aichhorn, Jan Philip Sindel, Amit Reza